This invention concerns devices for positioning body organs during x-ray examination. More specifically, this invention concerns fixtures for axially compressing a pendant breast during tomographic mammography procedures.
Cancer of the breast is a leading killer of American women. Experience indicates that this desease is most readily treated following early detection of malignent tumors. A major effort is, therefore, under way to provide large scale screening for symptoms of this condition among the female population.
Experience has shown that metastatis generally occurs in breast tumors between 1 and 3 centimeters in diameter. The x-ray density resolution of mammograms (photographic x-rays of the breast) is generally inadequate to distinguish breast tumors of less than 3 centimeters in diameter. Recently developed x-ray tomographic techniques allow electronic imaging of internal tissue density distributions with far greater resolution than is possible with photographic techniques. These techniques are described, for example, in U.S. Pat. Nos. 3,778,614 to Hounsfield and 3,881,110 to Hounsfield et al. A copending U.S. Pat. application, Ser. No. (RD-8312) by R. Redington and J. Henkes (which is assigned to the assignee of this patent application) describes the use of tomographic x-ray techniques for the detection of tumors in pendant breasts and is hereby incorporated by reference in this disclosure.
In accordance with the above referenced copending United States patent application, the detection of tumors in the periphery of the breast may be enhanced by immersing the breast in a fluid medium having x-ray transmission characteristics which are substantially equal to those of soft human tissue. A mixture of water with surfactants and antifoaming agents has been found to be ideally suited for this purpose.
Tomographic x-ray techniques reconstruct sectional images of body tissue from multiple measurements of x-ray transmission characteristics along a plurality of paths through a plane in the tissue. A relatively large number of x-ray exposures, as compared to photographic techniques, are necessary for the development of tomographic image of the breast. Patient's safety dictates that the number of x-ray images, and therefore the total radiation exposure, be minimized during these procedures.